Component A is diffusing in a medium B. The flux N_A relative to a stationary point is equal to the flux due to molecular difusion, if

ANS:D - there is equimolar counter diffusion.

The flux 𝑁𝐴NA​ relative to a stationary point is equal to the flux due to molecular diffusion if there is equimolar counter diffusion. Equimolar counter diffusion occurs when two components, in this case A and B, are diffusing in opposite directions at the same rate. This results in no net movement of either component relative to a stationary point, as the movement of one component is exactly balanced by the movement of the other component in the opposite direction. As a result, the flux of component A relative to a stationary point is equal to the flux due to molecular diffusion. So, the correct option is:

• there is equimolar counter diffusion.